Exciter (effect)

An exciter (also called a harmonic exciter or aural exciter) is an audio signal processing technique used to enhance a signal by dynamic equalization, phase manipulation, harmonic synthesis of (usually) high frequency signals, and through the addition of subtle harmonic distortion. Dynamic equalization involves variation of the equalizer characteristics in the time domain as a function of the input. Due to the varying nature, noise is reduced compared to static equalizers. Harmonic synthesis involves the creation of higher order harmonics from the fundamental frequency signals present in the recording. As noise is usually more prevalent at higher frequencies, the harmonics are derived from a purer frequency band resulting in clearer highs. Exciters are also used to synthesize harmonics of low frequency signals to simulate deep bass in smaller speakers.

Originally made in valve (tube) based equipment, they are now implemented as part of a digital signal processor, often trying to emulate analogue Exciters. Exciters are mostly found as plug-ins for sound editing software and in sound enhancement processors.

Aphex started selling the professional units, and introduced two low-cost models: Type B and Type C. The Aural Exciter circuit is now licensed by a growing list of manufacturers, including Yamaha, MacKenzie, Gentner, Emu and Bogen. The original Aphex Aural Exciter, first offered in 1975, came without the Big Bottom circuit, which was added in 1992. Later revisions of the Aphex Aural Exciter included the Model 104 Type C and Type C2 units. Aphex released in 2001 [1] the Model 204 Aural Exciter and Optical Big Bottom, yet another refinement of the original unit. According to Aphex, the Model 204 updates the Aural Exciter and Big Bottom processor blocks with improved circuitry, including an optical gain-control element for the Big Bottom compressor.

Functionally similar units from competing manufacturers are generically known either as "psychoacoustic processors", "psychoacoustic exciters", "harmonic exciters", or "enhancers". In the 1990s and 2000s, broadly comparable products now available from BBE, Joemeek, SPL and Behringer. Most are analogue signal processors, although a few digital units began to appear in the 2000s. The BBE Sonic Maximiser utilises a similar process of frequency-dependent phase shifting, as do other brands to a varying extent.